Medicines Q&As
Q&A 17.5a
Can acetarsol be used to treat proctitis?
Prepared by UK Medicines Information (UKMi) pharmacists for NHS healthcare professionals
Before using this Q&A, read the disclaimer at www.ukmi.nhs.uk/activities/medicinesQAs/default.asp
(Date prepared: May 2013)
Background
Acetarsol (an organic arsenic derivative) was formerly given orally in the treatment of intestinal
amoebiasis and vaginally in the treatment of trichomoniasis. The use of arsenic compounds is now
largely superseded.(1) However, acetarsol suppositories for intractable proctitis, still has a place in
therapy when other treatments have failed.(2)
Answer
There have been two small studies looking at the use of acetarsol suppositories for proctitis.
A double blind trial involving 44 outpatients was carried out to assess the efficacy of acetarsol
compared to prednisolone-21-phosphate suppositories (Predsol) in the treatment of idiopathic
proctitis.(3) Treatment was randomly allocated by the pharmacist to either Predsol 5mg suppositories
or acetarsol 250mg, two at night for 3 weeks. Only 40 patients are reflected in the results since 4
patients (3 on prednisolone, 1 on acetarsol) did not attend for follow-up examination. Results are in
the table below.
Prednisolone-21-phosphate
(n=23)
Symptoms after treatment for 3 weeks
None
8
Improved
7
Unchanged
2
Worsened
3
Total
20
Sigmoidoscopic appearances after treatment for 3 weeks
Improved, non haemorrhagic
11
Improved, still haemorrhagic
6
Unchanged
3
Total
20
Acetarsol
(n=21)
14
4
2
0
20
15
4
1
20
Patients’ symptoms and sigmoidoscopic appearances usually corresponded, and using both
assessment criteria, the results favoured acetarsol. One patient on acetarsol became jaundiced after
2 weeks of therapy. Treatment was stopped and the jaundice cleared rapidly. It is not certain if there
was causal relationship.
In a prospective open study, 10 patients with intractable proctitis were treated with acetarsol
suppositories (250mg twice a day for 4 weeks).(4) The study examined the systemic absorption of
arsenic as well as the effects on proctitis. Previous treatment for at least 4 weeks with oral
sulphasalazine or mesalazine plus twice daily corticosteroid enemas had failed. With acetarsol
therapy, proctitis resolved symptomatically and sigmoidoscopically within 2 weeks in nine patients.
Transient thrombocytosis occurred in one patient, perhaps related to active inflammatory bowel
disease rather than to arsenic, which tends to cause thrombocytopenia.
From the NHS Evidence website www.evidence.nhs.uk
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Medicines Q&As
The table below shows the blood and urine arsenic concentrations (microgram/L, medians and
ranges).
Sample
Prior to treatment
After 1 week of treatment
After 4 weeks of treatment
1 week after completing
treatment
4 weeks after completing
treatment
Blood
<10 (0-13)
48 (18-123)
18 (2-160)
Urine
26 (7-70)
6550 (1440-12580)
1380 (38-6080)
9 (4-15)
49 (29-69)
4 (1-6)
45 (41-78)
The maximum blood concentration observed was 160µg/L at 4 weeks in a single patient, but the
highest level was observed at 1 week, when the rectal mucosa remained obviously inflamed. Six
patients had a urinary inorganic arsenic level considered hazardous in forensic practice (>200µg/L)
after 1 week’s therapy. This remained hazardous in two patients after 4 weeks but both blood and
urinary arsenic concentrations fell rapidly after treatment was stopped. This showed that arsenic is
absorbed systemically from acetarsol suppositories. The fall in blood and urine concentrations
between weeks 1 and 4 suggest that absorption, initially facilitated by permeable inflamed mucosa, is
limited as the proctitis resolved. Adverse effects from arsenic concentration are unknown. Forbes et
al did not find any clinical consequence from this but cannot recommend long-term therapy.
Summary
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The precise mechanism of action of acetarsol in proctitis is unknown.
Acetarsol suppositories have been used for proctitis for many years at St Mark’s Hospital
(Specialist Gastrointestinal unit).
Proctitis can affect both patients with Crohn’s disease and ulcerative colitis in principle but
proctitis is more likely in ulcerative colitis.(5)
The usual dose used is 250mg bd (up to 3-4 weeks), after other treatments have failed. Arsenic
is absorbed systemically but reduces as the proctitis resolves. No monitoring is necessary for
short term treatment.(2)
Limitations
The evidence is limited: There are only 2 small trials, the most recent of which is from 1989, and
included very few patients.
Disclaimer
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Medicines Q&As are intended for healthcare professionals and reflect UK practice.
Each Q&A relates only to the clinical scenario described.
Q&As are believed to accurately reflect the medical literature at the time of writing.
See NeLM for full disclaimer.
References
(1) Sweetman SC. Martindale: The Complete Drug Reference (online). Acetarsol (date of
monograph revision 23/09/2011). London: Pharmaceutical Press, 2013.
(2) MiDatabank enquiries: 42467, 44678, 45525, 50150, 55384, 93014.
(3) Connell AM, Lennard-Jones JE, Misiewicz JJ. Comparison of acetarsol and prednisolone-21phosphate suppositories in the treatment if idiopathic proctitis. The Lancet 1965; i:238-239.
(4) Forbes A, Britton TC, House IM et al. Safety and efficacy of acetarsol suppositories in
unresponsive proctitis. Aliment Pharmacol Therap 1989; 3:553-556.
(5) Pharmacy Manager (J Eastwood), St Marks Hospital. May 2013. Personal communication
From the NHS Evidence website www.evidence.nhs.uk
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Medicines Q&As
Prepared by
Varinder Rai [based on earlier work by Wynn Pevreal and Caroline Fletcher], London Medicines
Information Service (Northwick Park Hospital)
Date Prepared
Updated May 2013
Checked by
Alexandra Denby, London Medicines Information Service (Northwick Park).
Date of check
20th May 2013
Contact
nwlh-tr.medinfo@nhs.net
Search strategy
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Medline – 1950 to date. [acetarsol.af] [Limit to: Human and English Language and Publication
Year 2011-current]
Embase – 1980 to date [ACETARSOL] [Limit to: Human and English Language and
Publication Year 2011-current]
MiDatabank – acetarsol (past enquiries)
NHS Evidence www.evidence.nhs.uk
Clinical Specialist: Jackie Eastwood, Pharmacy Manager, St Marks Hospital.
From the NHS Evidence website www.evidence.nhs.uk
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